Sensors and Actuators B 246 (2017) 1039–1048 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo ur nal home page: www.elsevier.com/locate/snb Enhanced sensing properties of cobalt bis-porphyrin derivative thin ﬁlms by a magneto-plasmonic-opto-chemical sensor A. Colombelli a , M.G. Manera a,∗ , V. Borovkov b , G. Giancane c , L. Valli d , R. Rella a a IMM-CNR Institute for Microelectronic and Microsystems, Unit of Lecce, Campus Ecotekne, Via Monteroni, 73100 Lecce, Italy b Department of Chemistry, Faculty of Science, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia c Department of Cultural Heritage, University of Salento, Via D. Birago, 73100 Lecce, Italy d Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento Campus Universitario Ecotekne, Via Monteroni, 73100 Lecce, Italy a r t i c l e i n f o Article history: Received 22 July 2016 Received in revised form 24 January 2017 Accepted 27 January 2017 Keywords: Gas sensor SPR-MOSPR Magneto-optical signal Co-porphyrins Langmuir–Schäfer a b s t r a c t This work reports on the spectroscopic properties and gas sensing performances of cobalt bis-porphyrin derivative ((Co-H)Por 2 ) in a thin ﬁlms form obtained by Langmuir–Schäfer (LS) method towards Volatile Organic Compounds (VOCs) and an oxidizing gas in a Magneto-Optical Surface Plasmon Resonance (MO-SPR) conﬁguration. In particular the optical and spectroscopic properties of (Co-H)Por 2 multilayers deposited onto proper Au/Co/Au magneto-plasmonic (MP) transducers were inspected in dry air con- ditions and after exposure to different analyte gas concentrations. The molecular organization of these thin ﬁlms deposited by Langmuir–Schäfer technique has been investigated and a comparison between the MOSPR experimental data and simulation has been also reported. In order to validate our experimental results and obtain further insight into the physical mechanism of interaction between the organometallic molecules and magneto plasmonic nanostructured systems, numerical simulations based on Finite Element Method (FEM) techniques, have been performed. The optical and magneto-optical properties of these hybrid systems have been theoretically analyzed to con- ﬁrm the experimental outcomes. Finally, a peculiar sensitivity of the MOSPR sensing probe in respect to investigated analytes has been recorded. © 2017 Elsevier B.V. All rights reserved. 1. Introduction So far, sensor technology has been receiving a great interest in the realization of materials suitable for chemical sensor devices because of a possibility to perform rapid and low cost screening of various analytes in order to satisfy the emerging demand from various ﬁelds of life, such as industrial control, environmental mon- itoring, medicine, foodstuff production and testing. Our attention has been recently focused on volatile organic compounds (VOCs) such as alcohols and amine, as well as NO 2 oxidizing gas, owing to their essential role in monitoring food and beverage processing [1,2]. Porphyrins represent a large family of functional molecular materials with high chemical and thermal stability. These com- pounds are object of great interest for chemists, physicists and industrial scientists because of their potential role in emerging technologies including photoconductors, solar cells and chemical sensors [3–6]. ∗ Corresponding author. These macrocycles, when deposited as thin ﬁlms, interact with some oxidizing and reducing gases and VOCs by various adsorp- tion processes of gas or vapor molecules onto the sensing layer [7]. The gas-surface interaction leads to reversible changes of some physical properties of the organic molecular thin ﬁlms which can be monitored by different technological methodology like quartz microbalances, surface acoustic wave devices, surface plas- mon resonance excitation, optical absorption change, electrical conductivity, and other measurements [8]. Different transducers have been proposed for the porphyrin-based sensors, showing outstanding properties in terms of stability, chemical sensitivity, and reproducibility. In order to be exploited as sensing materi- als, porphyrin compounds usually need to be deposited onto an appropriate substrate as solid ﬁlm. To date for this purpose, a large number of different chemical techniques (for example, solvent casting, spin coating, Langmuir–Blodgett, electro-polymerization, self-assembled monolayers) have been utilized and studied [9–11]. Generally, compounds possessing an extended -electron cloud, such as porphyrins, display semiconducting characteristics and exhibit intense absorptions in the UV–vis spectral region. Upon exposure to certain analytes, these substances experience signiﬁcant variations of their electrical and optical properties, thus http://dx.doi.org/10.1016/j.snb.2017.01.192 0925-4005/© 2017 Elsevier B.V. All rights reserved.